5-316 L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
GROUPED ELEMENTS CHAPTER 5: SETTINGS
5
DD CONTROL LOGIC — Used to prevent operation of I_0 and I_2 logic of disturbance detector during conditions such as
single breaker pole being open that leads to unbalanced load current in single-pole tripping schemes. Breaker auxiliary
contact can be used for such a scheme.
DD LOGIC SEAL-IN — Used to maintain disturbance detector output, 50DD SV, for such conditions as balanced three-phase
fault and low level time overcurrent fault, whenever the disturbance detector might reset. 50DD SV is maintained until the
chosen FlexLogic operand resets.
DD SEAL-IN BY 87LG — Used to seal-in the disturbance detector output, 50DD SV 87LG, especially for the 87LG element
whenever the 50DD SV might reset before 87LG time delay elapses. 50DD SV 87LG is maintained until the 87L DIFF PKP G
operand resets.
DD VOLTAGE SUPV — Used to enable the voltage-based disturbance detector for such applications as the weak condition
exists at one terminal, where the weak-infeed current is not able to trigger the current-based disturbance detector. The
voltage signals used for this detector are taken from the source assigned with the
CURRENT DIFF SIGNAL SOURCE 1 setting.
DD EVENTS — This setting can be disabled when the disturbance detector element responds to any current disturbance on
the system that results in filling the events buffer and possible loss of valuable data.
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